Trimming attachment for sewing-machines



(No Model.)

T; C. ROBINSON.

TRIMMING ATTACHMENT FOR SEW ING MAGHINBS.

No. 286,153. Patented Odt. 2, 1883.

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MM 1 l UNITED STATES PATENT OFFICE.

THOMAS C. ROBINSON, OF BOSTON, MASSACHUSETTS.

TRIMMING ATTACHMENT FOR SEWING-MACHINES.

SPECIFICATION forming part of Letters Patent No. 286,153, dated October2, 1883,

To all whom it may concern:

Be it known that I, THoMAs G. ROBINSON, of Boston, in the countyofSuffolk and State of Massachusetts, have invented certain Improvementsin Trimming Attachments for Sewingdllachines, of which the following isa specification.

This invention relates to sewing-machine trimming attachments employingrotary blades working in slots in the bed or throatplate of the machine.

My invention has for its object to enable a blade of this class, whilerotating on an arbor j ournaled in fixed bearings, to operateintermittently, and also to provide inter1nittently-actingpressure-regulating devices to *press the cutting-edge of the rotatingknife against a fixed cooperating blade only when said rotat-V ingcutting-edge is in position for operation.

To these ends my invention consists in the improvements which I will nowproceed to describe and claim.

Of the accompanying drawings, forming a part of this specification,Figure 1 represents a side elevation of a'W'illcoxdsGibbs sewingmachineprovided with my improved attachment. Fig. 2 represents a sectionthrough the bed of the machine, showing a side view of the rotary knife.Fig. 3 represents a top view of my attachment.

The same letters of reference indicate the same parts in all thefigures.

In the drawings, (t represents a slot in the throat-plate of themachine, and 1) represents a fixed shear-blade secured to a fixed partof the machine, and forming a part of one side of said slot. I

0 represents a rotary blade affixed to an ar bor, d, which is journaledin fixed bearings e e, and has at its rear end apinion, f, meshing witha pinion, g, on the drivingshaft h of the machine. The blade 0 issubstantially diskshaped, with an offset, 0, at one side. One edge ofsaid offset is sharpened, and forms a cuttingedge extending from 2 to 3,Fig. 2, said cutting-edge extending outside of theperiphery of the bodyof the blade, and being formed to assume substantially the same relationto the fixed blade b, in passing the latter, that the edge of anordinary vertically-reciprocating trimming-lmife, assumes to the fixedblade with which it cooperates. It will be Application filed June 9,1883. (No model.)

seen, therefore, that the cutting-edge of the rotary blade cooperateswith the fixed. blade, and cuts the material interposed between saidblades intermittently, or once during each ro tation of the blade. Aportion of the periphery of the blade a constantly projects sufficientlyinto the slot a to prevent the material being trimmed from passing underthe blade beyond the point where it is cut by the cooperatingcutting-edges.

' The described devices constitute a cheap and efficient trimmer, easilyapplied to a machine of the kind shown, and entirely independent 6 ofthe head or arm of the machine. Heretofore a rotary-disk trimmer hasbeen made havinga cutting-edge extending continuously around itsperimeter and journaled in fixed bearings. Said cutterbeing always incontact with the work partially obstructs the feed movements of thesame. A disk-trimmer has also been intermittently operated byalternately raising and lowering it while in operation; but suchintermittent operation involvcs complication of mechanism and expensewhich are avoided by. my improvement. I prefer to give the arbor d aslight freedom of longitudinal movement, and provide it with a cam, t,having a swelled or thickened portion, 2", corresponding in position tothe cutting-edge of the blade 0. Said thickened portion comes in contactonce during each rotation of the arbor d, and while the cuttingedge ofthe blade 0 is cooperating with the fixed blade I), with a fixedprojection, j, on the frame of the machine. Said projection is in thepresent instance an adjustable screw, and when it comes in contact withthe thickened portion of the cam it exerts endwise pressure on the arbor(Z through said cam, andthu's causesthc cuttingedge of the rotary cutterto impinge against the fixed blade in the same manner that the movablecutting edge is pressed against the fixed blade in the inventiondescribed in Letters Patent issued to me June 5, 1883, No. 278, 825. Assoon as the cutting-edge ofthe rotary bladehas performed its work, thethickened portion of the cam passes away from the projection j and the1' endwise pressure ceases, so that there is no marked friction of themoving parts, excepting during the cutting operation.

I claim- 1. In a sewing-machine, the combination of j the rotary blade,and intermittently-acting dethe throatplate having a slot and a fixedblade at one side thereof, a shaft or arbor rotated in fixed bearingsabove the bed of the 5 machine, and a rotary blade affixed to saidarbor, and having a perimeter projecting continually into said slot, andan offset cuttingedge, forming a part of said perimeter, co-opcratingonce during each rotation of the shaft to with said fixed blade, theprojection of the perimeter of the rotary blade into the slot preventingthe displacement of said blade from its operative position with relationto the fixed blade, as set forth.

2. Asewing-machinc provided with a shaft or arbor rotated in fixedbearings, a rotary blade afiixed to said arbor, and provided with anoffset cuttingedge adapted to act intermittently, a slot in thethroat-plate or bed, into o which said blade projects, a fixed blade atone side of said slot, adapted to co-operate with vices for pressing therotating cutting-edge against the fixed blade only when said blades arein co-operation, as set forth.

3. The combination, witha sewing-machine having a slot, at, in itsthroat-plate, and a fixed blade, I), at one side or edge of said slot,of the shaft h, journaled in fixed bearings,and

adapted to be rotated by the driving-shaft of 30 the machine, the blade0, affixed to the arbor, projecting into the slot a, and having theoffset cutting-edge c, the cam i, affixed to said shaft, and theadjustable bearing j for said cam, as set forth.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this'7th day of June, 1883.

. THOMAS C. ROBINSON.

- Witnesses:

O. F. BROWN,

A. L. WHITE.

